It's the mammalian diving reflex - we hold our breath if our face is submerged in water I wouldn't try it if you're not confident, but if you feel Ok about it try Look at baby, say "Fred, ready, go" and sprinkle water on his head Repeat, this time wiping a wet hand across his face Then say the same thing, this time lift the baby up slightly then firmly but carefully submerge, while holding upright, then bring up out of the water and lean over your shoulder slightly Never lean the baby back as they will get water up their nose